1. Field of Inventions
The present inventions relate generally to medical devices that support one or more diagnostic or therapeutic elements in contact with body tissue and, more particularly, to methods of deploying helical devices that support one or more diagnostic or therapeutic elements.
2. Description of the Related Art
There are many instances where diagnostic and therapeutic elements must be inserted into the body. One instance involves the treatment of cardiac conditions such as atrial fibrillation and atrial flutter which lead to an unpleasant, irregular heart beat, called arrhythmia.
Normal sinus rhythm of the heart begins with the sinoatrial node (or xe2x80x9cSA nodexe2x80x9d) generating an electrical impulse. The impulse usually propagates uniformly across the right and left atria and the atrial septum to the atrioventricular node (or xe2x80x9cAV nodexe2x80x9d). This propagation causes the atria to contract in an organized way to transport blood from the atria to the ventricles, and to provide timed stimulation of the ventricles. The AV node regulates the propagation delay to the atrioventricular bundle (or xe2x80x9cHISxe2x80x9d bundle). This coordination of the electrical activity of the heart causes atrial systole during ventricular diastole. This, in turn, improves the mechanical function of the heart. Atrial fibrillation occurs when anatomical obstacles in the heart disrupt the normally uniform propagation of electrical impulses in the atria. These anatomical obstacles (called xe2x80x9cconduction blocksxe2x80x9d) can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets, called xe2x80x9creentry circuits,xe2x80x9d disrupt the normally uniform activation of the left and right atria.
Because of a loss of atrioventricular synchrony, the people who suffer from atrial fibrillation and flutter also suffer the consequences of impaired hemodynamics and loss of cardiac efficiency. They are also at greater risk of stroke and other thromboembolic complications because of loss of effective contraction and atrial stasis.
One surgical method of treating atrial fibrillation by interrupting pathways for reentry circuits is the so-called xe2x80x9cmaze procedurexe2x80x9d which relies on a prescribed pattern of incisions to anatomically create a convoluted path, or maze, for electrical propagation within the left and right atria. The incisions direct the electrical impulse from the SA node along a specified route through all regions of both atria, causing uniform contraction required for normal atrial transport function. The incisions finally direct the impulse to the AV node to activate the ventricles, restoring normal atrioventricular synchrony. The incisions are also carefully placed to interrupt the conduction routes of the most common reentry circuits. The maze procedure has been found very effective in curing atrial fibrillation. However, the maze procedure is technically difficult to do. It also requires open heart surgery and is very expensive.
Maze-like procedures have also been developed utilizing catheters which can form lesions on the endocardium (the lesions being 1 to 15 cm in length and of varying shape) to effectively create a maze for electrical conduction in a predetermined path. The formation of these lesions by soft tissue coagulation (also referred to as xe2x80x9cablationxe2x80x9d) can provide the same therapeutic benefits that the complex incision patterns that the surgical maze procedure presently provides, but without invasive, open heart surgery.
Catheters used to create lesions typically include a relatively long and relatively flexible body portion that has a soft tissue coagulation electrode on its distal end and/or a series of spaced tissue coagulation electrodes near the distal end. The portion of the catheter body portion that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the coagulation electrode contacts the tissue that is to be ablated. Fluoroscopic imaging is used to provide the physician with a visual indication of the location of the catheter.
In some instances, the proximal end of the catheter body is connected to a handle that includes steering controls. Exemplary catheters of this type are disclosed in U.S. Pat. No. 5,582,609. In other instances, the catheter body is inserted into the patient through a sheath and the distal portion of the catheter is bent into loop that extends outwardly from the sheath. This may be accomplished by pivotably securing the distal end of the catheter to the distal end of the sheath, as is illustrated in U.S. Pat. No. 6,071,279. The loop is formed as the catheter is pushed in the distal direction. The loop may also be formed by securing a pull wire to the distal end of the catheter that extends back through the sheath, as is illustrated in U.S. Pat. No. 6,048,329. One lesion that proved difficult to form with conventional steerable and loop devices was the circumferential lesion that is formed within the pulmonary vein, or in the tissue surrounding the pulmonary vein, which isolates the pulmonary vein and cures ectopic atrial fibrillation.
More recently, helical structures have been developed that can be used to create circumferential lesions within or around bodily orifices and, in the context of the treatment of atrial fibrillation, within or around the pulmonary vein. Various examples of such helical structures are disclosed in U.S. application Ser. No. 09/832,612, which is entitled xe2x80x9cHelical And Pre-Oriented Loop Structures For Supporting Diagnostic And Therapeutic Elements In Contact With Body Tissue.xe2x80x9d These structures are particularly advantageous because they may be used to create lesions within or around the pulmonary vein without occluding blood flow.
Heretofore, helical structures have been deployed within a patient by inserting them through a sheath in a collapsed state to a region that is adjacent to, and preferably aligned with, the target bodily orifice. The collapsed structure was then urged distally out of the sheath (or the sheath was retracted), thereby allowing the collapsed structure to assume its helical shape. Next, the helical structure was urged distally into contact with the tissue surrounding the orifice. With respect to the pulmonary veins, the helical structure was deployed within the left atrium and then urged distally into contact with the tissue associated with the pulmonary vein ostium.
The inventor herein has determined that, while useful, the conventional method of deploying a helical structure within a patient is susceptible to improvement.
A method of deploying a helical structure having at least one operative element within a bodily structure defining an orifice in accordance with one embodiment of a present invention includes the steps of inserting at least a portion of the helical structure through the orifice in an uncoiled state and returning the helical structure to a coiled state while at least a portion of the helical structure is within the bodily structure such that the coiled helical structure engages the orifice. Such a method typically results in superior tissue-operative element contact at the orifice than does coiling the helical structure in spaced relation to the orifice and then advancing the helical structure distally into contact with the orifice.
The deployment method is particularly useful in the treatment of a pulmonary vein with a tapered helical structure having one or more operative elements on the proximal coils. Here, the helical structure may be inserted into the pulmonary vein ostium prior to being returned to its coiled state. The tapered helical structure will deploy into the funnel-shaped ostium of the pulmonary vein in such a manner that the atrial tissue will distend and wrap around the helical structure as it wedges itself into position. So positioned, the operative element(s) will be forced against the pulmonary vein ostium and, as a result, tissue coagulation will only occur at the ostium and the likelihood of thermally activated in-vein stenosis will be reduced.
The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.